They may have similar calories per ounce—158 for pumpkin and 164 for sunflower—but pumpkin seeds pack 68 percent more tryptophan, an amino acid that aids in the production of serotonin, a mood-regulating neurotransmitter. Pumpkin seeds also offer more than five times as much magnesium per cup; a recent study found that postgrad students whose diets regularly met or exceeded their RDA for magnesium (320 milligrams for women, or roughly half a cup of pumpkin seeds) were less likely to be depressed than students whose diets contained the least.